LTE services demand infrastructure changes

LTE services demand infrastructure changes

John Spindler, director of product management at Tyco Electronics, on the world of LTE.

LTE services promise a new world of higher data access speeds and new, advanced applications, but LTE networks will require major infrastructure changes to work properly.

While traditional large cells can provide urban coverage, they can’t deliver the capacity that LTE will require of the network. Rather than continuing with traditional large tower, macro cell infrastructure that has served them until now, mobile operators will have to adopt new, small cell infrastructure.

Wanted: Fatter pipe

Advanced applications such as augmented reality and video will require far more capacity in the network, and this is where new services like LTE come in. Published estimates by Vodafone and other major carriers suggest that LTE service will range from 5-12 Mbps on the downlink and 2-5 Mbps on the uplink. This is far greater than the 0.8-1.2 Mbps downlink and 0.2 – 0.4 Mbps on the uplink promised for 3G services such as UMTS and HSPA. As a result, each of the subscribers in a given area will need 5-10 times as much available data capacity. Making cells smaller is the only way to deliver higher capacity per cell.

Sectorising, or breaking up a large cell into smaller ones, has been a common practice among carriers for several years in areas where capacity demands outstrip network capabilities. This situation typically occurs in dense urban areas or large public venues (airports, stadiums, etc.) where an unusually high concentration of cell phone users demands network services at the same time.

With LTE, which is all about wireless data, the capacity crunch will extend to more areas than ever before. Along with stadiums and transit hubs, we will see capacity constraints in city centre’s, suburban shopping malls, office buildings, universities, hospitals, and many other locations. But by deploying a higher number of smaller cells, carriers can provide adequate capacity for everyone under LTE.

Cell + DAS = Happiness

The problem is that cells are expensive to deploy and each cell requires its own backhaul connection to the network. To overcome these issues, the best practice in deploying a small-cell infrastructure is to combine small cells with distributed antenna systems (DAS).

DAS extend the reach of cell base stations by delivering the base station signals through a series of small remote antennas. These antennas can be inside buildings, in parking lots, in underground subways or other structures, or they can be located in any outdoor areas where more coverage is required (such as urban canyons where the macro network signal is ‘shadowed’ by buildings). By extending the reach of the base station with DAS, capacity can be delivered precisely where it is needed.

Instead of requiring thousands of small base stations, DAS products simply extend a base station signal; they can carry whichever frequency the base station puts out. The more advanced active DAS products can deliver multiple frequencies and deliver the same high, uniform signal strength at every antenna, no matter how far it is away from the base station source.

Once deployed, DAS are virtually transparent to the network and are largely trouble-free. Their small antennas fit easily on the sides of buildings, in office ceilings, or even in street furniture, so they can be deployed in more places without objections from city planners. Since the DAS distribute the signal, base stations can be deployed at existing cell sites or in centralised ‘base station hotels’.

Sharing, caring and GSOH

Moreover, since DAS can distribute multiple frequencies, DAS infrastructure can be shared by more than one mobile operator. This way, operators can co-locate base stations in a central location and use a common DAS to distribute their signals to buildings or outdoor urban areas.

Using DAS to distribute signals in LTE networks will also end the traditional demarcation between in-building and outdoor networks. Extended DAS networks can serve both urban outdoor areas and inside buildings, allowing mobile operators to better integrate their various assets for unified management and control.

LTE will require a wholesale move toward small cell mobile infrastructure, and DAS will enable that infrastructure in a cost effective and highly efficient manner.